FET driver questions

I think you mean a so-called linear driver. The drivers from Convoy for example also use FETs but have a limited current. You recognize it because of the current limiting or sense resistor (R010, R020).

The most efficient ones are buck drivers or buck-boost drivers which convert the voltage and require less current if the voltage of the battery is high. The 7135 drivers just convert the eccessive voltage into heat. If a driver has a big grey thing on it like this one it is a buck or boost driver. The Lume1 driver from Loneoceans is a constant current buck-boost driver: Lume1-FW3X: Constant Current Buck-Boost & FET Driver with Anduril1/2 + RGB Aux

What would you need the driver for?

I am not a driver expert, I just know what I have read on BLF. Let’s see if some of the real experts can tell you more.